


Puzzle Box

by justmaybee



Category: Dr. STONE (Anime)
Genre: Alternate Universe - Canon Divergence, First Time, First Time Blow Jobs, Fluff and Smut, M/M, Shameless Smut, mostly lots of kissing, sengen
Language: English
Status: Completed
Published: 2019-10-20
Updated: 2019-10-20
Packaged: 2020-12-26 23:37:43
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,764
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21109061
Author URL: https://archiveofourown.org/users/justmaybee/pseuds/justmaybee
Summary: In the old world, Gen entertained himself by unraveling the psychological profiles of powerful people and using that knowledge to seduce them. Now he's up to his old tricks again, but Tsukasa proves especially hard to crack, and he isn't interested in the mentalist's games. He sends him after Senku instead, and Gen discovers there's more to sex than science ...





	Puzzle Box

**Author's Note:**

> Slight deviance from canon--characters are in university, not high school, some details about the plot are moved around. Also warnings for implied violence, and Gen being Gen (i.e. super manipulative).

Asagari Gen huffed impatiently. Tsukasa was interested, he was sure of it, but the man was intractable. Gen had initially expected a child celebrity: lonely, divorced from reality, starved for intimacy but wary of false friends. That profile had fallen apart within hours of his revival. Tsukasa was ... fascinating. A puzzle truly worthy of his efforts.

"Gen."

Gen looked up with a start. Tsukasa stared at him, hooded eyes unreadable to anyone who wasn't the world's leading mentalist. Gen offered an eager smile: the man wanted something from him, and that was all the opening Gen needed.

"Yes, dear Tsukasa?"

"I want you to find Senku."

This again. Tsukasa seemed to have exactly two subjects of conversation, and as one of the first to be revived Gen had had plenty of time to get acquainted with them. The first was Tsukasa's new world order. The second was the scientist, Senku.

"I'm afraid I'm no tracker, dear Tsukasa," Gen said, spreading his hands apologetically. 

"You know how people think," Tsukasa said. He turned his back on Gen, an infuriating habit that made it nigh impossible to flirt with him. "You can get inside his head."

Gen rolled his eyes. From what he'd learned of Senku from Tsukasa's brooding monologues and Senku's old friends, Gen had a fairly shrewd idea of how the man thought and where he might have gone. If indeed the scientist was still alive--and Tsukasa himself seemed only half convinced of the matter.

"You're fixating," Gen observed dryly. "If he survived, he must be severely injured. What threat could he possibly pose to the mighty Tsukasa ... ?"

Tsukasa flinched away as Gen touched his back. He glared at the mentalist, who performed his blandest, most innocent smile.

"Stop trying to--distract me," Tsukasa growled.

"Everyone needs a good distraction, dear Tsukasa," Gen breathed. "Now and again."

Tsukasa hesitated for a fraction of a second, eyes widening slightly. Then Tsukasa crossed his arms between them and looked away.

"Tonight," Tsukasa decided, his voice rough at the edges. "I want you to go. Find Senku. Spy on him. Report back to me."

"Of course," Gen murmured. "Tonight, dear Tsukasa."

As he walked away, down the winding path they had carved along the edge of the cliff, Gen felt Tsukasa's eyes on him. He did not need to look to know the man watched him hungrily, needily. Perhaps his profiling wasn't as misguided as he'd thought. Tonight ... yes, tonight would be the perfect time to go. He would go, and look for Senku, and when he found nothing he would return.

And when he returned, Tsukasa would be his.

Senku was alive. Gen couldn't quite fathom it, yet the wild-haired scientist looked no worse for having been turned to stone for 3000 years and then nearly killed by the world's strongest man. He was younger than Gen had pictured, a year or two younger than Gen's tender twenty-two years, with a smooth, youthful face and bone-white hair that stood inexplicably on end. After some brief unpleasantness, Senku had tried to bribe Gen to his side with cola of all things. It was cute, in a way, to watch the boy's fumbled attempts at deviousness. Baby's first mind games. Although of course, with a mind like Senku's, the boy hardly needed to play any games at all. 

Like Tsukasa, Senku's power lay in his conviction. Where Tsukasa imagined a world lead by the strong, Senku was actively working to level that world with science. Either one of them might have insisted they were aiming to build an amusement park, or a Fortune 500 company--the content of the dream was less important than their confidence, the way they talked and walked and looked at you.

"It will never work, you know, dear Senku."

If Tsukasa's gaze was brutal and cold, Senku's eyes were always dancing. The boy grinned at him over a beaker of something frothing. 

"It worked on you, didn't it?"

Gen laughed despite himself. Senku had that effect on people, he disarmed them. He made them careless. 

"Hope and promises," Gen sighed. "People are soft. We crave instant gratification, but civilization is hard work you know."

"You know that," Senku said, golden eyes suddenly still and solemn. "And I know that. But Tsukasa's following lived off the fruits of a millennia of hard work without ever coming face to face with that reality." The frothing liquid had begun to precipitate, filling the flask with an ashy substance. Senku set it aside, reaching for another ingredient without breaking stride. "They're hooked on science, and they'll do anything to get it. They just don't know it yet."

Hooked on science. Gen wanted to laugh at the cheesy line, to mock it, but he was ... distracted. The way the light fell Senku's neck, the way it got caught in his white eyelashes, Senku's total concentration as he moved through his makeshift laboratory. It was ... mesmerizing.

"If Tsukasa attacked tonight," Gen said suddenly. "What would you do?"

"Me?" Senku shrugged. "Probably run. Probably die. I'm no fighter. Why? Do you think that's likely?"

"... No." Gen admitted. He tucked his long, asymmetrical white bangs behind his ear. "He's frightened of you. Of what you can make. He won't lead any attack himself, and he won't send an attack without knowing he has the upper hand."

"Which is why he sent you, right?" Senku said. "To spy."

Gen grinned. 

"Dear Senku," he said, spreading his hands and letting his long sleeves fall back to his elbows. "You know me too well."

"No," Senku said. He caught Gen's gaze and held it. Gen's heart leapt. "I don't know you at all, Gen. That's the problem."

"Oh?" Gen had to get his pulse under control before he started blushing.

"We could rectify that. If you'd like."

Shadow crossed Senku's face as he picked up another flask, his features hard and inscrutable. Suddenly he reminded Gen of Tsukasa.

"I would," Senku said. "I'd like that quite a bit."

It had been a game for him, back in the old world, something to occupy his time. He would pick out somebody out of a crowd--the powerful CEO, the troubled heiress, the ageing diva--and he'd work them like a puzzle box. Pull on this insecurity, tweak that bias, and they'd come apart in his hands. Suddenly he would understand: complex, knotted, tangled people laid out so clean and simple, his to play with and discard. No point in keeping a puzzle you've already solved, after all.

Tsukasa was different. An unsolvable puzzle. A puzzle that solved you while you solved it. Gen laughed breathlessly as he picked himself off the ground. He couldn't help himself. It was exhilarating.

"I don't believe you," Tsukasa said, glancing at the back of his hand. The skin of his knuckles was thick and scarred from his days in the ring. Hitting Gen hadn't marked them at all. "You're too tricky for your own good, Gen. I'm beginning to wonder whether reviving you was a mistake."

"It's true," Gen said. "I've wondered why, of all the people you could have chosen, you picked a celebrity mentalist to help build your savage world."

"It was strategic."

"I'm sure you believe that," Gen said. "Dear Tsukasa."

"You lie the same way most people breathe," Tsukasa growled. "What did he promise you? No. It's not about promises, is it?"

Gen did not bother standing up. Given his current frame of mind, Tsukasa would only knock him back down again.

"I just don't believe there's a place for a man like me in a world like yours," Gen said.

Tsukasa paused, fists at his sides.

"There could have been a place," he said, softly. "I could have made one. For you, Gen."

Gen laughed.

"You, dear Tsukasa," he giggled. "Are a terrible liar."

Something clicked into place, and for a moment, Gen glimpsed the solution to the puzzle: Tsukasa stared at him, and something like fear sparked deep in those wide, wild eyes. Then the puzzle folded in on itself, and Tsukasa's face hardened.

"Fine," he said. "It doesn't matter. The world of science is dead. I killed its last survivor myself, and I'll do it again. Tonight. Run and warn him if you like. It makes little difference to me."

As Tsukasa strode from the cave, Gen staggered to his feet, rubbing his jaw. He was lucky Tsukasa hadn't broken it--no, not lucky. Had Tsukasa wanted to break it, he would have. He'd held back on purpose. He could have killed Gen here and now, but he hadn't. He wanted Gen to warn Senku. He wanted Gen to give him an excuse. Killing Gen didn't mesh with Tsukasa's self image. In fact, Gen would wager that the cognitive dissonance from killing Senku had nearly torn Tsukasa apart--and the tyrant would avoid another direct confrontation if he could. Gen could use that. 

No. _Senku_ could use that.

Gen broke into a dead sprint.

Months passed since that first assault. The specter of Tsukasa's aggression seemed to haunt the village, and yet--and yet somehow, Senku and Chrome, even Kohaku, they made time for joy amid the grueling labor that fueled Senku's scientific advancements. 

And for the first time in a long time, Gen was content. Helping Senku, talking to Senku, just being around Senku ... he needed no ulterior motive. Of course he had one anyway. Tsukasa was not wrong about him. Gen lied the way most people breathed: it was part of who he was.

"You want to go to space?"

He scrutinized the scientist's face for any sign the man was joking, but Senku met his gaze levelly.

"That's why we have to revive everyone," he said. "The whole world. Space travel exceeds what one isolated fragment of humanity can achieve."

"That's why ..." Gen laughed ruefully and shook his head. "You never cease to surprise me, dear Senku."

"_I_ surprise _you_?" Senku raised an eyebrow with a wry smile. They were sitting on a hill outside the village, watching as the first stars lit the purpling sky. Ramen bowls and pieces of Senku's latest experiment glittered in the grass: a beautiful failure, apparently. Gen had no idea what success would have looked like, but Senku had taken the setback in stride. _'Failure is just another step in the scientific process.'_ He would try again tomorrow, and Gen suspected that, one way or another, Senku would succeed. "I find that surprising. By now you must have a very thorough profile of me."

Gen considered feigning innocence, but found he was already smirking openly.

"I thought you didn't believe in psycho-analysis," Gen said.

"I'm a scientist, Gen," Senku said. "And what kind of scientist would I be if I didn't alter my hypothesis in the face of fact? Your skills are real."

"That, dear Senku," Gen murmured. "Was very nearly an ompliment-cay."

Senku began gathering up the bowls.

"Not a compliment," he said, his face lost in shadow. "Just an objective observation."

Gen watched him. Watched the way the muscles that corded his narrow frame moved under his shirt, watched the way his dexterous fingers stacked spoons and bowls and scientific instruments with an almost artistic precision. 

"Why do you want to go to space, dear Senku?"

Senku paused.

"Isn't it a very human dream?" he chuckled. "It's our most fundamental aspiration, to fly. To touch the heavens."

The sun had sunk below the horizon, revealing a handful of pinprick lights. More than had been visible in modern Japan at this time of the evening. Even a scientific simpleton could make that observation. 

"And you, Gen? What do you want?"

Gen smiled.

Gen folded his arms in his sleeves and watched the scientist from the corner of his eye. Senku was not a hard man to read. For someone so sharp, he was brutally and shockingly simple.

"How ..." Senku shook his head. The observatory was crude, but the villagers had done their best and the results went far beyond anything Gen could have hoped for. And in the absence of light pollution, the stars crowded the sky like wildflowers. Even without a powerful modern-day telescope, Senku would have a wonderful view.

"I already told you how," Gen said. "Even a scientific simpleton like me can do that kind of math."

Senku shook his head again.

"I meant--why," he said, but left the question unfinished. 

Senku might have been a brilliant scientist, but he was a psychological simpleton. Gen smiled at him, genuinely smiled, a smile that was rooted somewhere in his chest and grew through his whole body, filling him with warmth.

Their breath fogged the air and was swallowed by the night.

The villagers had gone to bed by now, and even Chrome had drifted off in the corner after exhausting himself in all his excitement over the observatory. With a few exceptions, the villagers were almost as simple as Senku. It was little wonder they had taken to him so quickly. A psychiatrist would have gone broke in a place ilk this. But for a mentalist, it was like getting let loose in a candy store with an endless supply of pocket change.

"Why ... ? Why indeed. I'd spell it out for you," Gen said. "But you'd think it was gross."

Senku stroked his chin, not quite hiding his smile. It was hard to tell in the dark, but Gen thought that smile was a little less confidant than usual, a little less sure.

Gen touched Senku's back. 

Senku leaned into the touch, ever so slightly.

"I have a hypothesis," Senku said, voice cracking on the last syllable and silencing him.

"Oh?" Gen ran his hand up Senku's spine and back again. The man was so skinny.

"I posit," he continued, voice dropping so low Gen had to lean in close to hear what he said. So close he could feel Senku's warmth. _So close._ "That you, that is, I. Um." Senku's eyes darted around, trying to find someplace neutral to rest. Someplace that wasn't Gen's eyes, or his lips.

Gen leaned in, until they were cheek to cheek.

"Go on," Gen murmured into his ear.

"Fuck it."

Senku kissed him. Hard and fast, artlessly, and yet--

They broke apart, breathless.

"That," Gen laughed. "Is a terrible hypothesis. Do it again?"

He held the back of Senku's head as they entwined, fingers tangling in the man's long hair. He lead this time, and he went slow and deep, until his lips ached. Transitioning away from Senku's mouth, he trailed kisses over his downy jaw and down his neck, pausing at the hollow of his collar bone, letting his teeth graze the skin before Senku pulled him back up to his mouth.

They froze as Chrome stirred.

"Maybe," Gen whispered, hoarsely. "We should take this somewhere more private."

Senku rolled his eyes helplessly but nodded. He took Gen's hand--roughly at first, but then gently, almost tenderly tugging him along. 

"Where--" Gen giggled. He felt drunk. He felt high. He wanted to kiss Senku's hand, kiss each long, chemical-stained finger. "Where are we going?"

"I have an idea," Senku said, eyes wide. His lips and cheeks were visibly flushed, even in the wane light of the moon.

Gen laughed again as Senku pulled him into the _lab_ of all places, and shut the door behind him. He pressed Senku against it, trapping him with his body. They were almost equal in height. Maybe Gen had an inch on Senku. Maybe not. He stroked Senku's hair, brushing aside the stray locks that fell across his eyes. 

"How do you get it so ... _tall?"_ he muttered, dazedly.

Senku pulled him into a kiss. He was getting the hang of it now, but Gen didn't care if their teeth clashed. He wanted Senku, wanted to drink him in until there was nothing left of either of them. Spinning away from the door, they landed on a pile of leather hides, and Gen wondered fleetingly what Senku wanted leather for as Senku pinned him. Their bodies met, and Gen felt every inch of Senku's exquisite length pressed up against him, felt the hard angles of his ribs and hips against his. 

"This," Senku panted, fumbling at Gen's collar. "How do you ... ?"

Laughing, Gen pulled the knot out, giving Senku full access. Senku grinned childishly, and began making his way down Gen's long neck, trailing his lips over the sensitive skin and migrating to his nipple, lavishing him with his tongue and menacing with the edge of his teeth. He worked the other with deftly, rolling it between his fingers until Gen wanted to scream, then switched sides. Gen shuddered deliciously.

"Enough," he announced, pushing Senku off him. "Take off your coat, Gen. Now."

Startlement vanished into hazy desire as Gen scrambled to get the coat off his body, careless of buttons and stays. After a long struggle, he threw the jacket off with a snarl. Dappled moonlight bathed his smooth chest and slender waist in silver shadow. Placing two fingers on Senku's slim shoulder, Gen pressed him down and straddled him. He leaned in close, closer, until their lips were a hair's breadth apart. Until a spark of static could have leapt the gap and joined them. Then he planted a kiss on Senku's nose with a wild whoop of laughter.

Senku stared in surprise. 

"Hey!" he laughed. Then, with a mock growl he pulled Senku back down to kiss him properly. Gen collapsed onto him. Their bodies met as one, skin to skin, sharing their warmth in the frigid winter night. He broke away from Senku's lips and kissed his cheek, then the corner behind his jaw. Then further down: the hollow of his neck, his chest, the slight curve of his pectoral. The thin line of fuzz that crossed his belly button. Further down. To the edge of his loincloth, where the fuzz began to coalesce into something more serious ...

He stopped, feeling Senku's hand tighten on the back of his skull. He could just make out Senku's eyes in the shadows, bleary and glittering, hungry but ...

"What's wrong?" Gen asked, kissing the swell of his belly gently. 

"I haven't. I mean. I don't ..."

Of course. The artless kissing. The total inability to voice even a hypothesis.

"But, I thought you and Taiju ... ?"

Senku laughed.

"Taiju--he's just, we're friends," Senku said. "Really good friends. But not like ..."

Not like this.

"But the way you talk about him," Gen insisted, fumbling through what they were about to do in his mind. What it might mean to Senku, or might not mean, or--

"Taiju's straight as a picket fence, dense as a lead weight," Senku sighed. "Don't get me wrong, I used to ... But he's been in love with this girl since we were kids. We're just friends."

_Just_. The word came out with a bitter twist. _Just_ friends.

"So you've never," Gen hesitated, watching Senku's face carefully. "Well. Never ... with a man?"

"What?" Senku laughed, a little too loudly. "Never what with a man, Gen? Never had sex? No. Never kissed? Never held hands?"

Gen flushed furiously, which seemed unfair--Senku should have been the one blushing. Maybe he was. It was hard to tell in the dark.

"We don't have to do this tonight," Gen said, sitting up. "Or at all. We could just stick to--to kissing."

"Kissing is nice," Senku said, a little hoarsely. "But there's one thing I've always wanted to try."

Gen raised an eyebrow.

"Fellatio."

Gen burst out laughing. 

"Sorry! Sorry, I'm not--of course we can try, ahah, ellatio-fay. Giving or--?" He didn't need to finish, as Senku was already pushing him off and flipping him onto his back. "Oh. _Oh!_ Ok."

Senku grinned, and kissed him, an excited, eager kiss. A distracting kiss, that went on and on. Senku was stalling. When he broke away, Gen held him close, stroking the side of his face with his thumb.

"Are you sure? I could do you first, or we could--"

"I want to," Senku said, kissing the base of Gen's thumb, kissing the inside of his wrist, and then his arm. "I _want_ to."

Gen helped him with his belt, with the knot. Senku's fingers trembled, or maybe Gen's fingers were trembling--it was hard to tell. Why would his fingers be trembling though? Gen had done this a thousand--

Senku's lips brushed across his pelvis and stopped at the base of Gen's dick. He'd been hard since they started, in the observatory, and it had been so long ... it jerked as Senku trailed his tongue up its length, flat across the head were he'd already begun to leak. He wrapped his tongue around it.

Gen's hips jerked and his hands knotted in Senku's hair.

He moaned as Senku took in more of him, as he could feel the hard roof of his mouth and the soft wetness of his tongue, as he could feel all of him, and then his lips tightened around the shaft. 

A mad white heat flooded through him, pulsing and irresistible: his hips bucked uncontrollably as Senku pulled back, savoring every inch. He went down again and Gen gasped, toes curling as he tried, desperately to hold back-- 

"D-dear Senku," he panted, and their eyes met: Senku, lips still wrapped around his head, golden eyes dancing as Gen squirmed and gasped under his touch.

He came suddenly, and without warning, an explosion that arched his back and burst from his lips in a long, wordless groan. He collapsed, heart thundering in his ears. Every muscle trembled. Sitting up, Senku lapped a long strand of cum off his fingers and made a face at the taste. Gen chuckled hoarsely. He pulled him down beside him, into his arms. 

"I never got to hear what your hypothesis was," Gen murmured into Senku's neck, breathing in the scent of smoke and sweat and something vaguely chemical. The scent of Senku.

"Doesn't matter. I'm a terrible scientist." Senku's laughter reverberated in his chest, under Gen's fingertips. "But I do get results."

"Hmmm. I suppose you do at that." Gen sat up. "Do you want me to do you?"

Senku stared up at him, still holding his hand.

"Um," he said, and now he was definitely blushing. "I kind of ... already came."

"Senku!" Gen laughed, pouncing on him. 

"What?" Senku snapped, then snickered. "The first experiment is never a complete success. Science is about perseverance."

"Then we'll just have to try again," Gen said, kissing Senku's nose. 

"Yes," Senku murmured. "Yes, I suppose we will."


End file.
